1. Field of the Invention
The invention relates to a Coriolis mass flowmeter with at least four bent measuring tubes, at least one actuator assembly and at least one sensor assembly, wherein a first measuring tube and a second measuring tube are located in a common first plane and a third measuring tube and a fourth measuring tube are located in a common second plane, wherein the first plane and the second plane run parallel to one another and wherein all four measuring tubes are joined together in terms of flow on the input side and on the output side with a collector.
2. Description of Related Art
According to the Coriolis principle, mass flowmeters have been known essentially for many years, they allow for a higher accuracy in the determination of the mass flow rate of the medium flowing through the measuring tube. In order to determine the mass flow rate, the measuring tube is excited to oscillation by an oscillation generator or also by multiple oscillation generators—in particular, a certain eigenform of an oscillation with the eigenfrequency—and the actual, resulting oscillations are detected and evaluated by oscillation sensors. The oscillation generators and the oscillation sensors are generally constructed in such a manner that they have a permanent magnet as well as a magnetic coil in order to transfer oscillations on the measuring tube or to detect oscillations of the measuring tube electrically.
The evaluation consists, for example, of determining the phase shift between each oscillation detected by the two oscillation sensors, wherein this phase shift is a direct measure for the mass flow rate. Coriolis mass flowmeters are known that have one, single measuring tube, as well as those having exactly two measuring tubes, wherein the measuring tubes are either stretched essentially straight or bent.
The measuring tubes of the mass flowmeter have very different nominal widths with different wall thicknesses depending on the amount of mass to be transported. The measuring tubes have to be configured in such a manner that they can withstand the required pressures and occurring mechanical tension, that they can be excited to an easily detectable oscillation with reasonable energy expenditure and the eigenfrequency of the measuring tube with flowing medium lies in a desired range.
German Patent Applicaton DE 10 2004 035 971 A1 and corresponding International Patent Application Publication WO 2006/010687 A1 disclose a Coriolis mass flowmeter with four bent measuring tubes, wherein the measuring tubes can each be supplied in pairs in direct flow or in reverse flow with a fluid whose mass flow is to be determined. The four measuring tubes are optionally, in units of two measuring tubes, arranged next to one another or above one another and can be commonly excited to opposing oscillations. Parts of an actuator or sensor assembly are affixed to a pair of measuring tubes, so that the measuring tubes can be excited to oscillation and the excited oscillations can be detected by the sensor assembly. In the arrangement, in which the measuring tubes are arranged above one another in pairs, the lower measuring tube is designed somewhat larger in order to span the longer path between input and output.